Transmission-regulating system for radio and carrier-telegraph systeme



Jan. 8, 1929. 1,697,905

. R. w. DEARDORFF TRANSMISSION REGULATING SYSTEM FR RADIO AND CARRIER TELEGRAPH SYSTEMS Filed OCT.. l, 1926 .K ATTORNEY "Pntente'd Jan. 8,1929. Y

vUNITE)STATES PATENT OFF v RALPH W. DEABDORFF, F SEATTLE, WASHINGTN',

l PHONEAND TELEGRAPH COMPANY, A CORPO 1,697,905 ica.

AssreNon To mamon 'rannaarron or maw You.

rmnsnrssromaneurnrme SYSTEM For. Ramo AND cnnnmn-mn-Lmnrn ssrmzs.

Application led October 1, 192,6. Serial No. 138,977.

This invention relates to a transmission regulating system for radio and carrier telelwhich Fi channel, utilizes a ra h s stems and articularly to a system df tilde tgfpe inwhichpthe gain of the amplifier is varied by .and in accordance with changes' in the signaling current itself to compensate for changes in the line characteristics.

In high frequenc telegraph s stems, which term is intende to include bot 1 radio and carrier systems, it has been customary to employ means for automatically changing the gain of the amplifiers inthe circuit to com ensate for changes in its transmission equiva ent. Heretofore it has been customary to transmit. a control current consisting of a single frequency, lying outside of the band of signaling frequencies, and to utilize this 'control current to operate the regulating device `by means of which the amplifier gain is varied. This control cur rent, which is termed in the art a pilot portion of the frequency spectrum that might otherwise be employed forv the transmission of signals. Consequently, if the re lation of the amplier gain'can be effecte b changesin the signalv voltagesthemselves, the use of a.- ilot channel is rendered unnecessary an a saving will result. T

The object of this invention is to control the amplifier gain in a radio or carrier telegraph system to com nsate for changes in the transmission equ1valent of the system,

the control being effected by means of the signal voltage itself. This invention will be clearly understood from the following description w en read in connection with the attached drawing, in re 1 shows schematically a form or embodiment of the invention, in which a lplurality of rela s responsive to currents of diierent strengt s control a regulating de vice connected with the amplier; Fig. 13L is a graph illustrating the o eration of Fig. 3'; lig. 2 is a form of em cdixnent of the invention in which a lurality of vacuum tubes perform substantlallyfthesame func-A tions as the relays in Fig. l; and Fig. 2 irs a graph illustrating the operation of i 2. C lign Figi. 1, 1 representsl a carrier telegraph transmitting devlce connected with the line L, for the'purpose of transmitting signals thereover tooperate direct current telegraph apparatus 2 `connected with the- The lines L1 and rectifier 3 and line L2. L, are connected b the the amp ifiere input side of the amplilier-rectier 3 is connected with 60 the potentiometer means of the controlled by 5 which may be varied by giin control device 6 which is t e relays 7 8 and 9, connected with the Wheatstone bridge 10. The gain control device 6,

cally in the drawing,

fication of a which is shown schematiis preferably a modi- Leeds and Northrup recorder described in the patent lto Leeds, 1,125,699, dated January 19, 1915, the modification consisting in the replacement of the pen, which is normally employed for the production of a record, with a contact point that en the wire of la potentiometer. electrlcal recorder is also described in tin No. 871 of the This ty e of ulle- Leeds and Northrup Com- ,75

pany, published in 1921. In an arrangement of that type, the flow of current through the coil 11 in a given direction will cause the arm 12 to move in a definite direction, and

the magnitude of its motion will be depend- 00 ent-upon the strength of the current in the coil. Likewise a 'through the coil reversal of the current 11 will cause the arm 12- to move in the opposite direction. The

elay4 4 is of the ordinaryy type relay which will r current above thereby transmit.

relays, 4, 7, 8 andI 9 are included in the 85 palate circuitv of the 'amplifier-rectifier 3. of telegraph ond` to a ran e .of

and be ow normal, an' will av marking impulse over 0o ph lays each having plate circuit of the tube 3, and having the other o5 winding connected with a source of biasing.

current. Thus relay crate at al mils "7 is ,biased to opabove the normal signal- -lng current, and when it operates its armature moves downward. Re operate at ai m11s below ay y8 is biased to 100 the normal current and upon operation its armature moves upward. Relay 9 is designed to operate at `all values of current, and when doing so its armature moves upward. The

function of the last mentioned relay will be clear from the subsequent y description. The Wheatstone bridge network 10 coni-prises the condensers -13 and 14, resistances il and 16,

and the source of potential 17. The 'operatf no posits to the operation of relay 7. The arm 12 willing winding 11 of the gain controldevice 6 is connected by means of conductors 18 and 19 with the resistances 15 and 16.

The manner in which this system operates to control the gain of the amplifier 3, in order to compensate for variations of the transmissionequivalent, is as follows: Let

it be assumed that Ithe -device 1 is sending signaling impulses, the marking impulses consisting of a train of waves of the signaling frequency and the spacing impulses consisting in a suppression of the signaling frequency. The impression of a trainof waves constituting a marking impulse upon the grid of the tube 3 will produce a flow of current in the plate circuit thereof which will ow through the winding of the various relays. f this resultant plate current is normal, the relay 4 will operate and transmit a marking impulse to the receiving device 2. Relay 7, which operates only on abnormally high currents, will not be operated but relays 8 and 9 will operate and cause their armatures to touch their contacts. The Wheatstone bridge 10 will. however, remain balanced and consequently, current will not flow through the winding 11 of the control device 6 difference exists across the contacts of lconductors 18 and 19 with resistances 15 and 16. If, however, the transmission equivalent changed so that the incoming signaling imulse produced a plate current 'which was mils above normal, the relay. 7 would operate, which would short-circuit the condenser 13 and unbalance the bridge, causing g current to iow from the source 17 through the resistance 15, which would produce a voltage across the conductors 18 and 19 and cause current to flow in a predetermined direction through the winding 11. This in turn would effect a movement of the arm 12 in such direction as to4 diminish the plate current of the tube 3, and thus restore to normal the current flowing through the relays 4, 7, 8 and 9. As soon as such a condi- `tion isy established, relay 7 will be de-energized, the short-circuit around the condenser 13 will be removed and vice 6 will cease to operate. That is to say, its arm12 will come to rest. In like manner, if the plate currentdrops more than a mils below normal, relay 8 will release and will short-circuit condenser 14, thus causing a flow of current through the resistance 16, and by virtue of the potential difference'established across the conductors 18 and 191will'cause current to iowthrough the winding 11, the direction ofwhich is opthat vof the current resulting from accordingly be removed in order to increase the current in the plate circuit ofthe tune 3. When the current is restored to normal because no potential the gain control dey8, the condenser 14 would be short-circuited when nothing was received from the line, and the device 6 would function by virtue of the unbalancing ofthe network 10. Re-

lay 9 therefore ceases to operate when signals are noty being received from the line, and opens the circuit which includes the contact of relay` 8. This is clearly shown in Fig. 1a where relay 9 is represented as operatingv and remaining operated upon current of small magnitude; relay 7 `will operate upon the normal current plus a current represented by a mils above normal; and relay 8 will operate upon current of a mils below normal.

In the arrangement shown in Fig. 2, in which the same reference characters have been employed as in Fig..1, the -regulation of the control devic'e 6 is effected by means of the vacuum tubes 3, 30 and 31. rill/he potentiometer 5, which is controlled by the arm 12 of the device 6, is connected not only with the grid of the tube 3 but also with the rids of the tubes 30 and 31. A source of plate potential 2O is connected between the filament of each tube and the plate of each tube, and each connection includes a winding of the polar relay 21. Thus the plate circuit of the tube 30 includes the winding 22 which is shunted by the resistance 23, the plate' circuit of the tube 21 includes the winding 24, and the similar circuit of the tube 3 includes the winding 25 of the relay 21, and also the operating Winding of the,

telegraph relay 4. As in Fig. 1, relay 4f i.

serves to control the transmission of signals over the line L2 to the recevingdevice 2.

rll`he polar relay 21 has its armature and Contacts and sources of potential so con-' nected with the winding 11 of the device 6 that whenl the armature is upon one contact ,current will flow through the winding 11 in a predetermined direction, and when Thus-thebattery C, app ie's a nega'- tive voltage m to the tube 30, the battery@2 tials upon the grids will be raised applies a voltage y to the tube 31, and the ybattery C3 applies a voltages to the tube 3.

The mode of 'operation of this system is as follows: Whena normal signal, as shown in Fig. 2,`is applied by means of the line L1 to the grids of thevarious tubes, the potento y. The resultant current in the platecircuit of the tube 30 will be equal to o and at the same instant the current in the plate circuit of the tube 3 will beequal to d, while the current in the-plate circuit of tube 31 is zero. The windings 22 and 25` of the polar relay 21, which are in the plate circuits of the tubes 30 and 3, respectively, are poled oppositely and the shunt 23 is so varied that the current lowingthrou h the winding 22 will equal that lowing't rough the winding whereby the fiux produced by one winding equals that produced by the other windin and the armature of the relay 21 is una ected. Accordingly, the winding 11 ofthe device 6 is not energized and no motion is given tothe arm 12 which controls the contact of the potentiometer 5.

Assuming that a signal greater than normal, such as shown in Fig. 2a, is impressed uponthe potentiometer 5 by the line L1, the grid potentials upon all of the tubes will be aand the resultant plate currents are as follows: that of tube being e, of tube 3, f, and of tube 31, g. Due to the shunt 23, that portion of the current e owing through the winding 22 will neutralize the effectY of the current f iiowing through the winding 25. The iiow of current g through the winding 24 causes the armature of relay 21 to move to its right-hand contact, thus causing current to flow from the source 26 through the winding 11 and causing the arm 12 to vary the potential applied to the grids of the various tubes. This arm will continue tomove until the potential is restored to its normal vvalue y, whereupon current will cease to How throughthe winding 24 and the currents in the will eiectively neutralize each other. The

control device 6 will cease to operate and' currents "of normal value will flow over the line L2 -to the ap aratus 2. If the signal falls below, norma the currents in the various plate circuits and in the polar relay Y windings are clearly shown in Fig. l2*.

Therewill be no current in winding 24 connected, with the output side of the tube 31. The current in winding 22 in the output side of tube 30, which is i ater than the current inwinding 26 in t e output-side of* tube 3, represented by j. yThe shunt 23 is adjusted to ualize thecurrent'v in windings 22 and'25 or normal sig nals only. .As thus adjusted, 'it will not ualize theleurrents for subnormal signals.

e eective' diiferenceA between h and j causes thev arglnatllxreA 21, tomovegto its leftwindings 22 and 25' cillations are transmitted,

represented by Ah, is

l voltage hand contact, thereby causing the gain control device v6 to move the contact of the potentiometer 5 in the direction to increase the signal volta as applied to the grids of the tubes. T e gain control device will continue to function until the potentiometer is `moved to such pointas to bring the signal strength to normal.

It will accordingly be seen that by means of the vinvention embodied in the arrangements shown in Figs. 1 and 2, the-gain of the amplifier connected with the circuit over which high frequency telegraph signals are being transmitted. may be varied in order to compensate for Ichanges of the transmission equivalent of the circuit.

While the invention has been disclosed as embodied in a wire carrier system, it is to be understood of course, that the line L1 may be replaced by a radio link, that is to say, the sending device 1 may be connected with a transmitting antenna and the potenl "tiometer 5 may be connected with a receiving antenna. Further variations may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

at is claimed is:

1.' In a carrier telegraph system, the combination with a source of alternating current voltage the amplitude of which may vary from normal of a plurality of' thermionic rectiers having similar grid voltage-plate current characteristics but each havin a grid biasing voltage diiering from the ot ers, an electro-magnetic switching device having a winding individual to and connected with the output circuit of each rectifier, the said windings being so arranged that the device is unoperated for normal plate currents, and voltage controlling means connected with 'the input of said rectiers and responsive to the operation of the said .switching edevice whenever the al- `terna'ting current voltage departs 'from'normal, thereb tending to restore the input voltage of t ve said rectiers to normal.

`2. In aarrier telegra h system, the combination with a source o carrier oscillations of a medium over or through which the osa receiving circuit connected with the said medium comprising a' plurality Voi? vacuum tubes having similar grid voltage-plate currentcharacteristics, each tube being normally biased by a grid voltage diering A:from that ofthe other tubes,switching means connected with the outputcircuitsof all of said tubes, the said means being unoperated when normal plate currents low therethrough but adapted to operate upon abnormal plate currents, and 4controlling means connected across the input of'said tubes, the said voltagecontrolling means responding to the operation of the 'said switchlng means. f

3. In a telegraph system in which a mark f is transmitted by a train ot waves of fixed normal amplitude .and a space by the suppression of such waves, or vice-versa, the combination with a plurality. of vacuum tube rectitiers having approximately the same grid voltage-plate current characteristic, of a source of alternating'current connected with the grid of ea^ h tube, a grid biasing source individual to and connected with the grid ot each' tube, the voltage ot one ot' said sources being internufrliate the voltages et the other sources, a polar relay having' a piurality of windings individual tothe said tubes and connected with the plate circuits thereof, the winding connected with the tube having the intermediate grid voltage being poled oppositely to the winding connected with the tube having the maximum negative biasing voltage, a non-polar relay connected with the plate circuit ot the tube of intermediate grid voltage, a gain-control device connected with the armature and contacts of the polar relay, and a potentiometer variable with changes of the .said gain con'- trol device to vary the potential ot' the alternating current applied to the said vacuuni tubes.

4. In a telegraph system in which a mark is transmitted by a train oit waves ot" fixed normal amplitude and a space by the sup-- pression ot said waves, or vice versa, the combination with a source of alternating current of a plurality of vacuum tube rectitiers having their input circuits connected in parallel with the said source, all of said tubes having substantially the same grid vvoltage-plate current characteristic, means to bias negatively the grid of each tube, the

degree of bias of one of said tubes being` intermediate that of the other tubes, anelecbeine' poled oppositely to the winding con` nectd with the tube of lowest grid voltage,

and means to equalize the currents flowing through the two last mentioned windings. `5. In aitelegraph system in which a mark is transmitted by a train of waves of fixed normal amplitude and a space by the suppression of such waves, or vice versa, the combination with a plurality of vacuum tube rectifiers of a source of alternating current connected with the input circuits of the said tubes,.all of said tubes having substantially the same grid voltage-plate current characteristic, means to bias negatively the grid ot each tube, the degree of bias ot one -tube being intermediate that of the other tubes, the ditlerence in voltage between the lowest biasing potential and thel intermediate potential being approximately equal to the normal voltage of the alternatingv current source, an electro-responsive device having a winding individual to each plate circuit, the winding connectedwith the tube having the greatest biasing potential being poledoppositely to the winding connected with the tube of intermediate biasing and having means to equalize the currents in the said winding when the normal alternating voltage is applied to the grids of the tubes, and regulating means eontrolled by the said electro-responsive means to vary the input voltage ot' the tubes inversely with changes in the plate currents of the said tubes.

ln testimony whereof, l have signed my name to this specification this 11th day of September, 1926. l

RALPH W. DEARDORFF. 

